Rotork Skilmatic SI3 Fail-Safe Electro-Hydraulic Actuator

Overview

The Rotork Skilmatic SI3 is a spring-return, self-contained electro-hydraulic actuator designed for valves whose failure position matters to plant safety. It joins the simplicity of electrical wiring with the smooth force of hydraulics and the dependable fail-safe stroke of a mechanical spring. Rotork describes the SI range as designed primarily for applications where functional safety is paramount, and the SI3 is the standard offering for quarter-turn valves up to 36 kNm and linear valves up to 235 kN.

Seven Star LLC supplies the Rotork Skilmatic SI3 for emergency shutdown valves, pipeline isolation, wellhead and gas processing duties across the Sultanate of Oman and the GCC. Our Muscat team checks the torque and thrust figures, spring direction and temperature option against the datasheet, and prepares a complete quotation including the documentation that safety engineers need.

Operating Principle

In normal operation the Rotork Skilmatic SI3 uses an electric motor to drive a hydraulic pump, which pressurises the cylinder and compresses the spring module as the valve strokes toward its powered position. On loss of the ESD signal or power supply, solenoid valves release the hydraulic pressure and the spring drives the valve to its fail-safe position. Operating times in the hydraulic direction are fixed by the pump option, while times in the spring direction can be adjusted between minimum and maximum values to limit surge.

Rotork lists three ways of configuring the fail action: loss of ESD or power supply, loss of ESD only, and loss of power only, with a stayput option for non fail-safe duties. The actuators can accept two ESD signals through an additional option card, which lets them respond to both a safety system and a process shutdown from the DCS without compromising the safety loop. Partial stroke testing is supported through a dedicated opto-isolated input.

Engineering Design of the Rotork Skilmatic SI3

The Rotork Skilmatic SI3 uses Rotork RH and GH quarter-turn actuators and LH linear actuators as the mechanical base. The cylinders are electroless nickel-plated, quarter-turn units use bronze sliding blocks and a floating piston seal to reduce friction, and spring modules can only be removed after all spring force has been released. Mechanical end stops provide plus or minus five degrees of stroke adjustment on quarter-turn versions.

The control module has a graphical display, local controls, a vibration sensor for logging 10 Hz to 1 kHz levels in three axes, and configurable home screens. Set-up is done through the Rotork Bluetooth Setting Tool Pro without removing covers. Enclosures are watertight to IP66/IP68 (7 m for 72 hours), and Rotork lists ATEX and IECEx Zone 1 certification with Ex db h marking for IIB and IIC gas groups, with ambient limits as low as -50 °C on selected builds.

Key Features

The Rotork Skilmatic SI3 is built for safety-instrumented valves that must be both reliable and testable. Key features of the Rotork Skilmatic SI3 include:

• Self-contained electro-hydraulic construction that needs only power and an ESD signal, with no external hydraulic power unit.
• Spring-return fail-safe action in either direction, with an inherently safe spring cartridge.
• Certification to IEC 61508:2010, SIL 2 capable without diagnostics and SIL 3 capable with diagnostics and partial stroke testing.
• Selectable fail modes, including loss of ESD, loss of power, both, or stayput.
• Quarter-turn output up to 36 kNm and linear thrust up to 235 kN for SI3, with SI4 reaching 200 kNm and 400 kN.
• Positional accuracy of 0.25 to 1 percent depending on actuator type, with on-off duty up to 15 cycles per hour.
• Graphical data logger, asset management and vibration trend logging that can be viewed on the display or downloaded through Rotork Insight 2 software.
• Network options including Pakscan, plus voltage-free relay outputs and independent limit switches for position and status indication.

Industrial Applications

Fail-safe valves guard the boundaries of oil and gas facilities, and the Rotork Skilmatic SI3 is a typical selection for pipeline emergency shutdown, wellhead control, high-integrity pressure protection and boiler fuel isolation. In remote Omani gas and oil fields, a self-contained actuator that needs no instrument air or hydraulic skid reduces both construction cost and the number of leak points. Operators with a hydraulic standard may also compare it with the Biffi RPD electro-hydraulic actuator when preparing a bid evaluation.

Seven Star LLC supports EPC contractors and plant operators in Sohar, Salalah, Duqm and the interior with engineering support in Muscat. Where a loop uses a smart positioner for partial stroke testing, such as the Masoneilan SVI II ESD positioner, we can discuss how the built-in PST of the Rotork Skilmatic SI3 compares. Non-safety isolation valves in the same plant may use the Rotork IQ3 for electric operation.

Technical Specifications

The table lists the main data from the Rotork Skilmatic SI range datasheet for the Rotork Skilmatic SI3. Individual actuator sizes have separate torque, thrust and timing tables in the datasheet.

Request a Quote for Rotork Skilmatic SI3

For a quotation on the Rotork Skilmatic SI3, send Seven Star LLC the valve torque or thrust, fail direction, ambient temperature range, ESD voltage and hazardous-area requirement. Our instrumentation division in Muscat will select the actuator size, confirm the operating times and attach the Rotork datasheet to the offer. Seven Star LLC supplies Rotork equipment on request with local engineering support across Oman and the GCC, so request your Rotork Skilmatic SI3 quotation today.